Proteinuria causes progressive kidney disease by impairing autophagy

描述（由申请人提供）：蛋白尿与进行性慢性肾脏疾病相关。众所周知，近端小管上皮（PTEC）细胞暴露于大量白蛋白会导致小管萎缩和纤维化。然而，白蛋白在这一过程中可能的致病作用尚未完全阐明。开发新的治疗工具来预防或减缓蛋白尿慢性肾病的进展需要清楚地了解蛋白尿对肾小管细胞功能的影响。我们提出PTEC暴露于白蛋白会抑制自噬，自噬是一种关键的细胞功能，负责细胞大分子和细胞器的更新，包括功能失调的线粒体。我们的假设是白蛋白通过以下机制之一损害自噬：(a)刺激白蛋白受体介导的信号事件；(b)上调mTOR，一种有效的自噬抑制剂；或(c)引起溶酶体功能障碍或抑制自噬体与溶酶体融合，从而抑制自噬。我们假设，通过白蛋白超载或敲低关键自噬蛋白对自噬的实验性抑制将导致功能失调线粒体的积累，从而增加活性氧的产生。由此产生的氧化损伤增加了线粒体膜的通透性和去极化，并促进线粒体内成分（如细胞色素c和AIF）的渗漏，这些促凋亡蛋白促进细胞死亡。在体内实验中，蛋白尿与自噬、ROS产生、PTEC凋亡、小管萎缩、纤维化和器官功能相关。我们将使用Ins2Akita/+，这是一种糖尿病小鼠模型，会出现蛋白尿、间质纤维化、小管功能障碍和萎缩。我们还将测试自噬的药理学上调是否能改善蛋白尿诱导的近端小管的变化。通过研究可能损害自噬的信号转导级联，本研究将提高我们对白蛋白在蛋白尿状态中致病作用的理解，蛋白尿状态是进行性慢性肾脏疾病的一个确定原因，并将研究自噬刺激剂在改善进行性器官衰竭中的新作用。掌握这个提案中提出的新的原理和技术对我的科学发展和未来的研究生产力至关重要。它们将补充我以前在实验室的经验，使我能够奠定一个独特的研究领域的基础，并帮助我在蛋白尿肾病领域的研究的深度和广度做出重大贡献。我相信这个NIH指导奖将促进我在科学上的成熟，并使我能够过渡到一个水平，使我能够竞争独立研究的支持。

DESCRIPTION (provided by applicant): Proteinuria is associated with progressive chronic kidney disease. It is well known that exposure of proximal tubular epithelial (PTEC) cells to large amounts of albumin leads to the development of tubular atrophy and fibrosis. However, the possible pathogenic role of albumin in this process has not been fully elucidated. Development of new therapeutic tools to prevent or slow the progression of proteinuric chronic kidney disease requires clear understanding of the effect of proteinuria on tubular cell function. We propose that exposure of PTEC to albumin inhibits autophagy, a critical cellular function responsible for turnover of cellular macromolecules and organelles, including dysfunctional mitochondria. Our hypothesis is that albumin impairs autophagy by one of the following mechanisms: (a) stimulating albumin receptor-mediated signaling events; (b) up-regulating mTOR, a potent autophagy inhibitor; or (c) causing lysosomal dysfunction or inhibition of autophagosomal-lysosomal fusion which, in turn, inhibits autophagy. We hypothesize that experimental inhibition of autophagy by albumin overload or by knockdown of crucial autophagic proteins will result in accumulation of dysfunctional mitochondria leading to increased production of reactive oxygen species. The resulting oxidative damage increases the permeability and depolarization of the mitochondrial membrane and facilitates the leakage of intramitochondrial components such as cytochrome c and AIF, pro-apoptotic proteins that promote cell death. In in vivo experiments, proteinuria will be correlated with autophagy, ROS production, PTEC apoptosis, tubular atrophy, fibrosis and organ function. We will use Ins2Akita/+, a diabetic mouse model that develops proteinuria, interstitial fibrosis, tubular dysfunction and atrophy. We will also test if pharmacologic up-regulation of autophagy ameliorates proteinuria-induced changes in the proximal tubule. By investigating the possible signal transduction cascades that impair autophagy, this proposal will improve our understanding of the pathogenic role of albumin in proteinuric states, an established cause of progressive chronic kidney disease, and will investigate the novel role of autophagy stimulators in ameliorating progressive organ failure. Mastering the new principles and techniques presented in this proposal is essential for my scientific development and future research productivity. They will complement my previous experiences in the lab, permit me to lay down the foundation of a unique area of research and help me make a significant contribution to the depth and breadth of research in the field of proteinuric kidney diseases. I believe that this NIH mentored award will promote my scientific maturity and allow me to transition to a level that will make me competitive for independent research support.